Photosynthesis, the natural process by which plants convert sunlight and inorganic matter into carbonates and oxygen, has long served as an inspiration for renewable energy research.

Despite its crucial role in sustaining life on Earth, natural photosynthesis is relatively inefficient (~1%) due to biological limitations. To remove this barrier, researchers developed a chloroplast-mimicking artificial photosynthetic cell (APC) that operates under mild conditions and achieves a solar energy conversion efficiency of 3.1%.

In a study published in Angewandte Chemie International Edition, Prof. WANG Yaobing and Dr. ZHOU Enbo from Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences, introduced an innovative APC design based on a molecular biomimetic thylakoid, CoTPP-FePy. This design was capable of splitting water into hydrogen (H₂) and oxygen (O₂) at a low driving voltage of 1.1 V (< 1.23 V) and near-neutral pH (≈7).

The researchers synthesized CoTPP-FePy, which combined cobalt-porphyrin (Co-TPP) as a water oxidation active site with covalently connected iron-pyridine (Fe^III/Fe^II-Py) shuttles as electron scavengers. Emulating the light reactions in natural thylakoid membranes, CoTPP-FePy effectively integrated light harvesting, photocatalysis, and electron/energy storage processes. Under illumination, CoTPP-FePy exhibited fast intermolecular charge transfer (580 fs) along with an extended excited state lifetime (>6.1 ns), effectively energizing the Fe^III-Py shuttles into Fe^II-Py and driving the water oxidation process at a rate of 35.5 μmol h^-1.

Furthermore, the researchers developed a novel photoelectrochemical water-splitting flow system that interfaced the light-driven process with thermochemical reactions. In the subsequent dark reaction mimic, the Pt-modified membrane-electrode assembly (MEA) drove hydrogen production, completing the electron/energy transfer cycle via the Fe^III/Fe^II-Py shuttles.

This study presents a fully chloroplast-mimicking approach that not only broadens the scope of research in biomimetic chemistry but also provides a promising and efficient way for solar energy utilization.